Thank you much for the thorough and thoughtful reply and for reviewing the selections!
I’d like to address the conclusions drawn of Get Lucky that seem off to me - that it is never-home and “out all night” 
If Get Lucky is to be taken in A major, the tonic is evinced – f#m7 has the notes F# A C# E which could easily be said to have tonic function considering the entire A triad is there, even voiced in close position. Wouldn’t I IV/ii ii IV still contain a lot of forward motion? It is unclear to me on what basis you deem bar 3 of Get Lucky to be hypermetrically weak while being okay with Cliffs of Dover’s bar 3. There’s no presence of some kind of rhythmic style that syncopates past the downbeat of 3, it is actually quite consistent from bar to bar. I do think steady meter and rhythm do provide a degree of flexibility and freedom which is why I stated my thoughts on Cliffs of Dover were a bit silly at the forefront. I don’t feel bar 3 here to be as hypermetrically weak as compared to say the first half of the progression in Bruce Hornsby’s “The Way It Is” with its unorthodox metric. Or am I misunderstanding what “weak” and “strong” is to be for this?
From all else though I think I’m starting to get the idea. You’d like modes to only be dignified as something to use in mode mixture of a scale perceived to be more important than the others when looking at 7 notes dividing an octave in Heptatonia Prima fashion, and it’s not about simple semantics between “mode” and “scale.” Although I find it weird you’d conceive “mode mixture within a mode” when earlier you said “Mixolydian scale” in reference to I bVII. An issue with this is with keeping the minor key distinction, although it is in essence another scale with an unique arrangement of intervals in the octave that is just known from borrowing conventions from major to bring a perceived stability to it. So this reduction seems hesitant and non-committal.
I understand that the major-anchored convention is scholarly used and accepted, and I actually do like it as a form of shorthand when communicating with those who I may know are already familiar with differences of scales, but you being used to this academic style guide could be the very thing that has brought you feel and claim that it is an easier approach specifically in relation to teaching. As someone not having spent extended time immersed in it, ease is far from a word I would use to describe it and I’ll try to elaborate why.
The minor label is redundant - there’s no point to the label of minor for say, i iv bIII bVII when the quality of the third degree is indicated by lowercase numeral i or dash (I- ), and flats are used in relation to major. As well, the use of flats in terms of major as if every chord is borrowed from Aeolian would suggest the I has been altered rather than inflect that we’re looking at a different kind of key. I feel I might as well scribble out the minor list from my circle of fifths print since it’s so suggestive that, if tonic is A, I’m to be looking at the 3-sharp signature. We could follow the trend of reduction away from autonomous scales even further and replace numerals with a scheme that refers to semitones in 12TET - like 0 2- 4- 5 7 9- 11o to represent the diatonic chords of our universal key, while not impeding on the ability to use the notation for other sets. This prospective [reverb+delay] nomenclature of the future [/fx] has the potential to satisfy both our contrary perspectives but it comes at the price of being completely disorienting and difficult to find trends and patterns. I’ll write out some simple progression loops in all 3 methods we’re discussing so we get some contrast.
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12TET
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0 7 9- 5
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0 9- 2- 7
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0- 10 3 5
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0- 5 2- 7-
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0- 1 3 1
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0- 3 1 10-
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0 7 9- 2
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0 4- 2 11-
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0 9- 10 5
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0 5 7- 10
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0- 10 8 10
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0- 5- 8 7
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Universal Key Popular Style
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I V VI- IV
- I VI- II- V
- I- bVII bIII IV
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I- IV II- V-
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I- bII bIII bII
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I- bIII bII VII-
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I V VI- II
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I III- II VII-
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I VI- bVII IV
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I IV V- bVII
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I- bVII bVI bVII
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I- IV- bVI V
Common Practice with Autonomous Scales
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TTSTTTS
- I V vi IV
- I vi ii V
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TSTTTST
- i VII III IV
- i IV ii v
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STTTSTT
- i II III II
- i III II vii
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TTTSTTS
- I V vi II
- I iii II vii
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TTSTTST
- I vi VII IV
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I IV v VII
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TSTTSTT
- i VII VI VII
- i iv VI V
Using subcategories to make some uniformity within the actual notation when it is used looks more intuitive and conducive to understanding to me. One can associate numerals to certain harmonic functions regardless of them being uppercase or lowercase (such as seen in one of Biamonte’s diagrams) and can clearly see for which cases such convention is broken without bogging by confusing extraneous symbols. You can point out reasons why major should be king with its stability in acoustic physics and strong influence in musical psychology and all that, but that would devalue music as an art form for expression that will not always generate familiar pleasing noises in perfect balance. Musicians themselves will be inclined to use the notation, and for them to find alterations with an inconsistency of where and how they’re used from song to song, when it rather should be explicitly noted another scale is at work, can be disincentivizing from exploring the amazing amount of possibility in 12TET alone and make it all the more likely they give up on implementing anything unorthodox with pitches for their personal expression, and just spew out I V vi IV because everyone else is. That’s not painting on a canvas, that’s coloring by number. Sure, one artist may color with glow in the dark neon while another may do pastel, but creativity is still limited by complications in comprehending the common threads of what is seen and hesitance to branch out beyond Heptatonia Prima because of the arbitrary crown put on a single scale.
I argue that compartmentalization (colloquial, not psychological) is known for making things easier to manage and is applicable here, in the way one may have a drawer to keep socks in, opposed to having socks interspersed within a pile of miscellanea. I would have assumed this is some kind of known principle in pedagogy.